Process for preparing thermostabilized trioxane-cyclic ether copolymers



United States Patent Int. Cl. C08f 15/58, 45/60 US. Cl. 260-67 8 Claims ABSTRACT OF THE DISCLOSURE There is disclosed herein a process for stabilizing a copolymer of trioxane and a cyclic ether by treating the copolymer in an aqueous buffered solution having a pH within the range of about 10.0 to about 10.5 at a temperature within the range of about 100 to about 160 C., the buffered solution containing, per 100 parts by weight of water, about 0.05 to about 1 part by weight of an aliphatic or a hydroxy-aliphatic amine, about 0.25 to about 2 parts by weight of urea or melamine and about 0.1 to about 1 part by weight of a weak organic acid or a weak inorganic acid.

This application is a continuation-in-part of application Ser. No. 464,198 filed June 15, 1965, now abandoned.

This invention relates to a process for preparing thermostabilized copolymers.

It is known that copolymers containing oxymethylene groups can be depolymerized at a high temperature in a non-aqueous solution or in an aqueous suspension under the action of a catalyst, for example, an alkali metal hydroxide or an alkaline earth metal hydroxide, and in the presence of a formaldehyde-intercepting compound, for example, a urea or diethanol amine, the depolymerization beginning at the end of a chain and stopping after reaching a mixing component.

Now we have found a process for stabilizing copolymers of trioxane and at least one cyclic ether of .the general formula in which R and R each represent hydrogen atoms or lower alkyl groups which can be substituted by halogen atoms, R represents a methylene group, an oxymethyleue group, a lower alkylor a halogen-lower alkyl-substituted methylene group, or a lower alkylor halogen-lower alkylsubstituted oxymethylene group, said lower alkyl groups having one or two carbon atoms, and n is an integer of 0 to 3, by treatment with an aqueous solution at a pH of about 10.0 to about 10.5 at a temperature within the range of about 100 to about 160 C., wherein the solution used contains a buflier system comprising about 0.05 to about 1 part by weight of an amine, about 0.25 to about 2 parts by weight of urea or melamine, and about 0.1 to about 1 part by Weight of a weak organic or inorganic acid per 100 parts of water in the solution. The weak organic or inorganic acid preferably has a first dissociation constant (k less than 2X10- if the acid is monobasic, less than 4x10- if the acid is dibasic and less than 2X if the acid is tribasic.

3,448,081 Patented June 3, 1969 Suitable copolymers are, for example, polymers of trioxane and about 0.05 to about 10 parts by weight per parts of trioxane of one or more cyclic ethers such as ethylene oxide, propylene oxide, epichlorhydrin, 1,4-butanediol formal, diethylene glycol formal, 1,4-butene-diol formal or 1,4-butane diol diglycidyl ether.

Amines that can be used are those corresponding to the following formula in which R represents a hydrogen atom, an alkyl group containing 1 to 5 carbon atoms or a hydroxyalkyl group containing 1 to 5 carbon atoms, R represent an alkyl group containing 1 to 5 carbon atoms or a hydroxyalkyl group containing 1 to 5 carbon atoms and R represents an alkyl group containing 1 to 5 carbon atoms or a hydroxyalkyl group containing 1 to 5 carbon atoms. Suitable amines are, for example, dimethyl amine, triethyl amine, tri-n-butyl amine or triethanol amine.

Suitable acids are weak organic or weak inorganic acids, especially those having a first dissociation constant less than 2 10 if the acid is monobasic, less than 4 10 if the acid is dibasic and less than 2 10 if the acid is tribasic. There can be used, for example, formic acid (k =1.77 10" acetic acid (k =1.76 10- oxalic acid (k =3.8 X10- barbituric acid (k =9.8 10- phthalic acid (k 1.2 X10 carbonic acid and boric acid (k =7.3 X 10- The k values are based on measurements of the dissociation constant at 25 C. The acid is used in an amount such that pH of the butfeted solution is within range of about 10.0 to about 10.5.

Suitable buffer solutions are, for example, those having the following compositions:

The reaction is advantageously carried out by suspending about 10 to about 100 parts by weight of the copolymer to be stabilized in about 100 parts by weight of an aqueous buffer solution of the kind described above and heating the resulting suspension for 15 to minutes under superatmospheric or autogenous pressure in an autoclave provided with stirring means to a temperature within the range of about to about C. When the reaction is terminated the cooled polymer is suction filtered, washed with water until neutral and dried in an oven under reduced pressure at a temperature within the range of about 50 to about 80 C. The stabilized products have excellent thermostability and do not undergo change of color.

If, instead of a buffer solution according to this invention, an aqueous solution of an amine and a urea is used, the polymers obtained are thermostable but their color will have changed.

The following examples serve to illustrate the invention but are not intended to limit it thereto, the parts being by weight.

EXAMPLE 1 120 grams of a copolymer of 98 parts of trioxane and 2 parts of ethylene oxidewere suspended in a solution of 591 grams of waters, 3 grams of triethyl amine and 6 grams of urea which had been adjusted to a pH of 10.3 by the addition of formic acid. The resulting suspension was heated for 30 minutes to a temperature of 145-147 C. in a glass autoclave having a capacity of 1 liter and provided with stirring means and oil circulation heating. The cooled, degraded copolymer was EXAMPLE 2 120 gramsof copolymer of 98 parts of trioxane and 2 parts of ethylene oxide were suspended in a solution of 591 grams of water, 3 grams of triethyl amine and 6 grams of urea which had been adjusted to a pH of 10.3 by the addition of acetic acid. The resulting suspension was heated for 30 minutes to a temperature of 145- 147 C. in a glass autoclave having a capacity of 1 liter and provided with stirring means and oil circulation heating. The cooled, degraded copolymer was suction filtered, washed with water until neutral and dried under reduced pressure at a temperature within the range of 50 to 70 C.

Yield grams 115 Loss of weight percent 0.0223 Color White EXAMPLE 3 120 grams of a copolymer of 98 parts of trioxane and 2 parts of ethylene oxide were suspended in a solution of 591 grams of water, 3 grams of triethyl amine and 6 grams of urea which had ben adjusted to a pH of 10.5 by the addition of oxalic acid. The resulting suspension was heated for 30 minutes to a temperature of 145 -174 C. in a glass autoclave having a capacity of 1 liter and provided with stirring means and oil circulation heating.

The cooled, degraded copolymer was suction filtered, washed with water until neutral and dried under reduced pressure at a temperature within the range of 50 to rams EXAMPLE 4 120 grams of a copolymer of 98 parts of trioxane and 2 parts of ethylene oxide were suspended in a solution of 594 grams of water, 3 grams of triethyl amine and 3 grams of urea which had been adjusted to a pH of 10.2 by the addition of barbituric acid. The resulting suspension was heated for 30 minutes to a temperature of 145-147 C. in a glass autoclave having a capacity of 1 liter and provided with stirring means and oil circulating heating. The cooled, degraded copolymer was suction filtered, washed with water until neutral and dried under reduced pressure at a temperature within the range of 50 to 70 C.

120 grams of a copolymer of 98 parts of trioxane and 2 parts of ethylene oxide were suspended in a solution of 591 grams of water, 3 grams of triethyl amine and 6 grams of urea which had been adjusted to a pH of 10.1

by the addition of boric acid. The resulting Suspension was heated for 30 minutes to a temperature of 145- 147 C. in a glass autoclave having a capacity of 1 liter and provided with stirring means and oil circulation heating. The cooled, degraded copolymer was suction filtered, washed with Water until neutral and dried under reduced pressure at a temperaturewithin the range of 50 to 70 C.

Yield -1. grams 151 Loss of weight percent 0.0197

Color White EXAMPLE 6 sion was heated for 30 minutes to a temperature of 145 147 ',C in a glass autoclave .havinga capacity .of 1 liter and provided withstirring means and oil, circulatidnheating. Thecooled, degraded copolymer was suction filtered, washed with water until neutral and dried under reduced pressure at a temperature within the range of 50, to 70 C.

Yield grams Loss of weight percent 0.0198 Color White EXAMPLE 7 grams of a copolymer of 98 parts of. trioxane and 2 parts of ethylene oxide were suspended in a solution of 591 grams of water, 3 grams of triethyl amine and 6" grams of melamine which had been adjusted to a pH of 10.1 by'the addition of boric acid. The resulting suspension was heated for 30 minutes to a temperature of -147 C. in a glass autoclave having-a capacity of 1 liter and provided with stirring means and oil circulating heating. The cooled, degraded copolymer was suction fil= tered, washed with water until neutral and dried under reduced pressure at a temperature within the range of 5 0 to"70"C. Yield grams 113 Loss of Weight percent 0.0198 Color White EXAMPLE 8 120' grams of a copolymer of .98 partsof trioxane and 2 parts of ethylene oxide were suspended in a solution of 597 grams of water and 3 grams of triethyl amine and heatedfor 30 minutes to a temperature of 145 -147 C. in a glass autoclave having a capacity of 1 liter and provided with stirring means and oil circulation heating. The cooled, degraded copolymer was suction filtered, washed with water until neutraland dried under reduced pressure at a temperature within the range of 50 to 70 C.

Yield grams 110 Loss of weight percent 0.0267

Color Brown EXAMPLE 9 A tion heating. The cooled, degraded copolymer was suction filtered, washed with water until neutral and dried-under reduced pressure at a temperature within the range of 5 0 to 70 C.

Yield 1grams 1 13 Loss of weight;- percent 0.0257

Color Yellow 5 EXAMPLE 10 120 grams of a copolymer of 98 parts of trioxane and 2 parts of ethylene oxide were suspended in a solution of 597 grams of water and 3 grams of triethyl amine which had been adjusted to a pH of 8.1 by the addition of C The resulting suspension was heated for 3-0 minutes to a temperature of 145 147 C. in a glass autoclave having a capacity of 1 liter and provided with stirring means and oil circulation heating. The cooled, degraded copolymer was suction filtered, washed with water until neutral and dried under reduced pressure at a temperature within the range of 50 to 70 C.

Yield grams 1 l 1 Loss of Weight percent 0.0382

Color Yellow We claim:

1. A process for stabilizing a copolymer of trioxane which comprises treating a copolymer of trioxane and a cyclic ether of the formula In which R and R each represent a hydrogen atom, an alkyl group or a halogen-substituted alkyl group, R represents a methylene group, an oxymethylene group, an alkyl-snbstituted methylene group, a halogen-alkyl-substituted methylene group, an alkyl-substituted oxymethylene group or a halogen-alkyl-substituted oxymethylene group, each of said alkyl groups having one or two carbon atoms, and n is an integer of 0 to 3, in an aqueous buffered solution having a pH within the range of about 10.0 to about 10.5 at a temperature within the range of about 100 to about 160 C., said buttered solution containing, per 100 parts by weight of water, about 0.05 to about 1 part by weight of an aliphatic or hydroxy-aliphatic amine having alkyl groups of 1 to 5 carbon atoms, about 0.25 to about 2 parts by weight of urea or melamine and about 0.1 to about 1 part by weight of a weak organic acid or a weak inorganic acid, the amount of said weak organic acid or said weak inorganic acid being such as to adjust the pH of said buffered solution to within said range of about 10.0 to about 10.5.

2. A process for stabilizing a trioxane copolymer according to claim 1 wherein said cyclic ether is ethylene oxide, propylene oxide, epichlorhydrin, 1,4-butane-diol formal, diethylene glycol formal, 1,4-butene-diol formal or 1,4-butane-diol diglycidyl ether.

3. -A process for stabilizing a trioxane copolymer according to claim 1 wherein said cyclic ether is ethylene oxide.

4. A process for stabilizing a trioxane copolymer according to claim 1 wherein said copolymer contains about 0.05 to about 10 parts by weight of said cyclic ether per parts of trioxane.

5. A process for stabilizing a trioxane copolymer ac cording to claim 1 wherein said amine is dimethylamine, triethylamine, tri-n-butylamine or triethanolamine.

6. A process for stabilizing a trioxane copolymer according to claim 1 wherein said weak organic acid or said weak inorganic acid has a first dissociation constant of less than about 2x 10 if it is monobasic, less than about 4 10-- if it is dibasic or less than about 2x 10* if it is tribasic.

7. A process for stabilizing a trioxane copolymer according to claim 1 wherein said weak organic acid or said weak inorganic acid is formic acid, acetic acid, oxalic acid, barbituric acid, phthalic acid, boric acid or carbonic acid.

8. A process for stabilizing a trioxane copolymer according to claim 1 wherein about 10 to about 100 parts by weight of said copolymer is treated per 100 parts of said buffered solution.

References Cited UNITED STATES PATENTS 3,174,948 3/1965 Wall et a1 260-67 3,198,852 8/1965 Tanner 260-45.85 XR 3,225,005 12/1965 Asmus et al. a 26067 WILLIAM H. SHORT, Primary Examiner.

L. M. PHYNES, Assistant Examiner.

US. Cl. X.R. 

